Methods and apparatuses for selecting beam in carrier aggregation

ABSTRACT

A radio terminal (2) receives beam configuration information from a base station (1), measures a plurality of transmission beams (10) transmitted from the base station (1) in accordance with the beam configuration information, and uses one or more beams selected from among the plurality of transmission beams (10) based on a measurement result as a serving beam. Each of the plurality of transmission beams carries a beamformed reference signal to be measured by the radio terminal (2). The beam configuration information includes a reference signal configuration indicating a radio resource used on each beam for transmitting the beamformed reference signal. It is thus, for example, possible to contribute to provision of a procedure for UE mobility between beams.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 16/906,024 filed on Jun. 19, 2020, which is acontinuation application of U.S. patent application Ser. No. 16/337,038filed on Mar. 27, 2019, which is a National Stage Entry of internationalapplication PCT/JP2017/018330 filed on May 16, 2017, which claims thebenefit of priority from Japanese Patent Application No. 2016-192329filed on Sep. 29, 2016, the disclosures of all of which are incorporatedin their entirety by reference herein.

TECHNICAL FIELD

The present disclosure relates to radio communication and, inparticular, to radio communication that uses directional beams.

BACKGROUND ART

The 3rd Generation Partnership Project (3GPP) has started to work on thestandardization for the fifth generation mobile communication system(5G), i.e., 3GPP Release 14, in 2016 to make 5G a commercial reality inor after 2020. 5G is expected to be realized by a combination ofcontinuous enhancement/evolution of LTE and LTE-Advanced and aninnovative enhancement/evolution by an introduction of a new 5Gair-interface (i.e., a new Radio Access Technology (RAT)). The new RATsupports, for example, frequency bands higher than the frequency bands(e.g., 6 GHz or lower) supported by the continuous evolution ofLTE/LTE-Advanced. For example, the new RAT supports centimeter-wavebands (10 GHz or higher) and millimeter-wave bands (30 GHz or higher).

In this specification, the fifth generation mobile communication systemis also referred to as a Next Generation (NextGen) System (NG System). Anew RAT for the NG System is referred to as a New Radio (NR), 5G RAT, orNG RAT. A new radio access network (RAN) and a core network for the NGsystem are referred to as a NextGen RAN (NG RAN) or a New RAN, and aNextGen Core (NG Core), respectively. A radio terminal (User Equipment(UE)) capable of being connected to the NG System is referred to as aNextGen UE (NG UE). A base station that supports the New Radio (NR) isreferred to as an NG NodeB (NG NB), an NR NodeB (NR NB), or a gNB. Thenames of the RAT, UE, radio access network, core network, networkentities (nodes), protocol layers and the like for the NG System will bedetermined in the future as standardization work progresses.

Further, the term “LTE” used in this specification includesenhancement/evolution of LTE and LTE-Advanced to provide interworkingwith the NG System, unless otherwise indicated. Suchenhancement/evolution of LTE and LTE-Advanced for interworking with theNG System is also referred to as LTE-Advanced Pro, LTE+, or enhanced LTE(eLTE). Further, the terms related to LTE networks and logical entitiesused in this specification, such as “Evolved Packet Core (EPC)”,“Mobility Management Entity (MME)”, “Serving Gateway (S-GW)”, and“Packet Data Network (PDN) Gateway (P-GW)” include theseenhancement/evolution to provide interworking with the NG System, unlessotherwise indicated. The enhanced EPC, MME, S-GW, and P-GW are alsoreferred to as, for example, enhanced EPC (eEPC), enhanced MME (eMME),enhanced S-GW (eS-GW), and enhanced P-GW (eP-GW).

As described above, the NG system supports higher frequency bands (e.g.,6 GHz or higher). In order to provide required coverage on these higherfrequency bands, higher antenna gain is required to compensate for pathloss. Meanwhile, since the size of an antenna element becomes smaller asthe wavelength becomes higher, a multi-antenna system using an extremelylarge number of antenna elements (e.g., several hundreds of antennaelements) can be implemented in a practical size in higher frequencybands. Accordingly, in the NG System, larger antenna arrays are used toform high gain beams. The beam means a radiation pattern at least havingseveral levels of directivity. High gain beams are narrower than widesector beams used in lower frequency bands (e.g., current LTE bands (6GHz or lower)). Accordingly, multiple beams are needed to cover arequired cell area.

NR NB may use a plurality of Transmission and Reception Points (TRPs). ATRP means a physical location for transmission and reception of radiosignals. TRPs may be arranged in a centralized manner or in adistributed manner. Each TRP may form multiple beams. The TRP may alsobe referred to as a remote radio head (RRH).

Several proposals regarding beam-related procedures in the NR systemhave been made (e.g., see Non-Patent Literature 1-6). The beam-relatedprocedures include mobility (procedure) and beam management (procedure)(Non-Patent Literature 6). The beam management is a set of layer 1(L1)/layer 2 (L2) procedures to acquire and maintain TRP(s) and/or UEbeams that can be used for downlink (DL) and uplink (UL)transmission/reception. The beam management at least includes beamdetermination, beam measurement, beam reporting, and beam sweeping. Thebeam determination is a procedure for TRP(s) or UE to select its owntransmission (Tx)/reception (Rx) beam(s). The beam measurement is aprocedure for TRP(s) or UE to measure characteristics of receivedbeamformed signals. The beam reporting is a procedure for UE to reportinformation regarding beamformed signal(s) based on the beammeasurement. The beam sweeping is an operation for covering a spatialarea with beams transmitted and/or received during a time interval in apredetermined way.

Further, it is assumed that the NR uses different sets of radioparameters for a plurality of frequency bands. For example, subcarrierspacing, symbol length, Transmission Time Interval (TTI), and subframeduration are different for frequency bands. These set of radioparameters are referred to as numerologies. In the NG system, the UE andthe NR NB support aggregation of multiple NR carriers with differentnumerologies. The 3GPP has studied achievement of the aggregation ofmultiple NR carriers with different numerologies by lower layeraggregation, such as existing LTE Carrier Aggregation (CA), or higherlayer aggregation, such as existing Dual Connectivity (e.g., seeNon-Patent Literature 7-9).

CITATION LIST Non-Patent Literature

[Non-Patent Literature 1] 3GPP technical document R2-163437, Nokia,Alcatel-Lucent Shanghai Bell, “Beam Terminology”, 3GPP TSG-RAN WG2Meeting #94, Nanjing, China, 23-27 May 2016

[Non-Patent Literature 2] 3GPP technical document R2-163443, Nokia,Alcatel-Lucent Shanghai Bell, “On beam sweeping and its implications”,3GPP TSG-RAN WG2 Meeting #94, Nanjing, China, 23-27 May 2016

[Non-Patent Literature 3] 3GPP technical document R2-163476, Nokia,Alcatel-Lucent Shanghai Bell, “Beam management in NR”, 3GPP TSG-RAN WG2Meeting #94, Nanjing, China, 23-27 May 2016

[Non-Patent Literature 4] 3GPP technical document R2-163579, IntelCorporation, “Mobility and beam support in NR”, 3GPP TSG-RAN WG2 Meeting#94, Nanjing, China, 23-27 May 2016

[Non-Patent Literature 5] 3GPP technical document R2-163712, Samsung,“Use cases and RAN2 issues of beam tracking in a beamforming based highfrequency NR”, 3GPP TSG-RAN WG2 Meeting #94, Nanjing, China, 23-27 May2016

[Non-Patent Literature 6] 3GPP technical document R1-168468, Nokia,Qualcomm, CATT, Intel, NTT DoCoMo, Mediatek, Ericsson, ASB, Samsung, LG,“Definitions supporting beam related procedures”, 3GPP TSG RAN WG1Meeting #86, Gothenburg, Sweden, 22-26 Aug. 2016

[Non-Patent Literature 7] 3GPP TR 38.804 V0.3.0 (2016 August) “3rdGeneration Partnership Project; Technical Specification Group RadioAccess Network; Study on New Radio Access Technology; Radio InterfaceProtocol Aspects (Release 14)”, August 2016

[Non-Patent Literature 8] 3GPP technical document R2-164788, Nokia,Alcatel-Lucent Shanghai Bell, “Carrier Aggregation between carriers ofdifferent air interface numerologies”, 3GPP TSG-RAN WG2 Meeting #95,Gothenburg, Sweden, 22-26 Aug. 2016

[Non-Patent Literature 9] 3GPP technical document R2-165328,“Aggregation of carriers in NR”, 3GPP TSG-RAN WG2 Meeting #95,Gothenburg, Sweden, 22-26 Aug. 2016

SUMMARY OF INVENTION Technical Problem

The inventor has studied UE mobility between beams and found someproblems. One of the objects to be attained by embodiments disclosedherein is to provide an apparatus, a method, and a program thatcontribute to provision of a procedure for UE mobility between beams. Itshould be noted that this object is merely one of the objects to beattained by the embodiments disclosed herein. Other objects or problemsand novel features will be made apparent from the following descriptionand the accompanying drawings.

Solution to Problem

In a first aspect, a radio terminal includes a wireless transceiver andat least one processor. The wireless transceiver is configured totransmit signals to a base station and receive signals from the basestation. The at least one processor is configured to receive beamconfiguration information from the base station, and to measure a firstplurality of transmission beams transmitted from the base station inaccordance with the beam configuration information. The at least oneprocessor is further configured to use, as a first serving beam fortransmission from the base station to the radio terminal, one or morebeams selected from among the first plurality of transmission beamsbased on a measurement result of the first plurality of transmissionbeams. Each of the first plurality of transmission beams carries abeamformed reference signal to be measured by the radio terminal. Thebeam configuration information includes reference signal configurationindicating a radio resource used on each beam for transmitting thebeamformed reference signal.

In a second aspect, a base station includes a wireless transceiver andat least one processor. The wireless transceiver is configured totransmit signals to a radio terminal and receive signals from the radioterminal. The at least one processor is configured to transmit beamconfiguration information to the radio terminal. The at least oneprocessor is further configured to use, as a first serving beam fortransmission from the base station to the radio terminal, one or morebeams selected from among a first plurality of transmission beamstransmitted from the base station based on a result of a measurement bythe radio terminal of the first plurality of transmission beams. Each ofthe first plurality of transmission beams carries a beamformed referencesignal to be measured by the radio terminal. The beam configurationinformation includes reference signal configuration indicating a radioresource used on each beam for transmitting the beamformed referencesignal.

In a third aspect, a method performed by a radio terminal includes: (a)receiving beam configuration information from a base station; (b)measuring a first plurality of transmission beams transmitted from thebase station in accordance with the beam configuration information; and(c) using, as a first serving beam for transmission from the basestation to the radio terminal, one or more beams selected from among thefirst plurality of transmission beams based on a measurement result ofthe first plurality of transmission beams. Each of the first pluralityof transmission beams carries a beamformed reference signal to bemeasured by the radio terminal. The beam configuration informationincludes reference signal configuration indicating a radio resource usedon each beam for transmitting the beamformed reference signal.

In a fourth aspect, a method performed by a base station includes: (a)transmitting beam configuration information to a radio terminal; and (b)using, as a first serving beam for transmission from the base station tothe radio terminal, one or more beams selected from among a firstplurality of transmission beams transmitted from the base station basedon a result of a measurement by the radio terminal of the firstplurality of transmission beams. Each of the first plurality oftransmission beams carries a beamformed reference signal to be measuredby the radio terminal. The beam configuration information includesreference signal configuration indicating a radio resource used on eachbeam for transmitting the beamformed reference signal.

In a fifth aspect, a program includes instructions (software codes)that, when loaded into a computer, cause the computer to perform themethod according to the above-described third or fourth aspect.

Advantageous Effects of Invention

According to the above-deceived aspects, it is possible to provide anapparatus, a method, and a program capable of contributing to provisionof a procedure for UE mobility between beams.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a configuration example of a radiocommunication network and one example of beam level mobility accordingto one embodiment of the present disclosure;

FIG. 2 is a diagram showing a configuration example of a radiocommunication network and one example of beam level mobility accordingto one embodiment of the present disclosure;

FIG. 3 is a diagram showing a configuration example of a radiocommunication network and one example of beam level mobility accordingto one embodiment of the present disclosure;

FIG. 4 is a diagram showing a configuration example of a radiocommunication network and one example of beam level mobility accordingto one embodiment of the present disclosure;

FIG. 5 is a sequence diagram showing one example of a procedure for UEmobility between beams according to one embodiment of the presentdisclosure;

FIG. 6 is a sequence diagram showing one example of the procedure for UEmobility between beams according to one embodiment of the presentdisclosure;

FIG. 7 is a sequence diagram showing one example of the procedure for UEmobility between beams according to one embodiment of the presentdisclosure;

FIG. 8 is a diagram showing one example of a user plane protocol stackfor aggregation of multiple carriers with different numerologiesaccording to one embodiment of the present disclosure;

FIG. 9 is a diagram showing one example of a user plane protocol stackfor aggregation of multiple carriers with different numerologiesaccording to one embodiment of the present disclosure;

FIG. 10 is a diagram showing one example of a user plane protocol stackfor aggregation of multiple carriers with different numerologiesaccording to one embodiment of the present disclosure;

FIG. 11 is a diagram showing one example of a user plane protocol stackfor aggregation of multiple carriers with different numerologiesaccording to one embodiment of the present disclosure;

FIG. 12 is a block diagram showing a configuration example of a basestation according to one embodiment of the present disclosure; and

FIG. 13 is a block diagram showing a configuration example of a radioterminal according to one embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Specific embodiments are described hereinafter in detail with referenceto the drawings. The same or corresponding elements are denoted by thesame reference symbols throughout the drawings, and repetitivedescriptions are omitted as necessary for clarity.

Each of the embodiments described below may be used individually, or twoor more of the embodiments may be appropriately combined with oneanother. These embodiments include novel features different from oneanother. Accordingly, these embodiments contribute to achieving objectsor solving problems different from one another and contribute toobtaining advantages different from one another.

First Embodiment

FIGS. 1-4 are diagrams showing several configuration examples of a radiocommunication network and several examples of beam level mobilityaccording to this embodiment. In the example shown in FIG. 1 , the radiocommunication network includes a New Radio (NR) base station (i.e., NRNodeB (NR NB)) 1 and a radio terminal (UE) 2. The NR NB 1 forms aplurality of transmission beams 10, and transmits a beamformed referencesignal (RS) on each of the transmission beams. In other words, each ofthe transmission beams 10 carries the beamformed reference signal. Thebeamformed reference signal may also be referred to as a beam-specificreference signal (BRS). The beamformed reference signal may be apre-coded Channel State Information (CSI) reference signal CSI-RS). Thebeamformed reference signal may be UE-specific or may benon-UE-specific.

The plurality of transmission beams 10 are specified by beam identifiers(beam IDs). In other words, the transmission beams 10 are distinguishedfrom one another by different beam IDs. The beam ID may also be referredto as a beam index. The beamformed reference signal may contain a beamidentifier. Alternatively, the beam ID may be specified by a radioresource or resources (e.g., a subcarrier, a time slot, a resourceblock, a spreading code, or any combination thereof) used fortransmitting the beamformed reference signal, or by an index associatedwith the radio resource or resources. In a case where one TRP forms onlyone transmission beam, the beam identifier may be a TRP identifier (TRPID). In other words, in place of the beam identifiers, TRP identifiersmay be used to distinguish the transmission beams 10 from one another.

The plurality of beam IDs of the plurality of transmission beams 10 maybe associated with the same cell identifier provided by the NR NB 1(e.g., E-UTRAN Cell Global ID (ECGI), Physical Cell Identifier (PCI)).In other words, the plurality of transmission beams 10 that cover thesame cell may be associated with the same cell identifier.

The UE 2 receives beam configuration information from the NR NB 1 in anyone of the cells managed by the NR NB 1, and measures the plurality oftransmission beams 10 of the NR NB 1 in accordance with the beamconfiguration information. The beam configuration information includesreference signal configuration indicating a radio resource used on eachtransmission beam 10 for transmitting the beamformed reference signal.The NR NB 1 and the UE 2 use, as a serving beam for transmission fromthe NR NB 1 to the UE 2, one or more beams selected from among theplurality of transmission beams 10 based on measurement results of theplurality of transmission beams by the UE 2. The selection (ordetermination) of the serving beam based on the measurement results ofthe plurality of transmission beams by the UE 2 may be performed by theUE 2 or by the NR NB 1.

For example, the NR NB 1 may transmit, in a cell of a lower frequencyband in which beamforming is not performed or a wide sector beam isused, the beam configuration information regarding the transmissionbeams 10 of another cell of a higher frequency band. The cell of thelower frequency band may be an (e)LTE macro cell and may be used tomaintain control connection between the NR NB 1 and the UE 2.Alternatively, the beam configuration information may be transmittedfrom the NR NB 1 to the UE 2 on a serving beam that has already beenselected (or configured). The beam configuration information transmittedon the serving beam may be used for a measurement of this serving beamand also used for a measurement and (re)selection of anothertransmission beam.

The beam configuration information may include a beam configuration setinformation element (IE). The beam configuration information may beincluded in any system information (System Information Block (SIB))broadcasted by the NR NB 1, or may be sent to the UE 2 via dedicatedRadio Resource Control (RRC) signaling. Alternatively, in a case wherethe UE 2 has beamforming functionality according to this embodiment andthe NR NB 1 supports (or activates) this beamforming functionality in aserving cell of the UE 2, the UE 2 may request the NR NB 1 to transmitthe beam configuration information. In response to the request from theUE 2, the NR NB 1 may broadcast the beam configuration information, ormay transmit the beam configuration information to the UE 2 viadedicated RRC signaling.

The beam configuration information may further include a beam identifier(e.g., beam ID, TRP ID). The beam configuration information may includean area configuration that corresponds to each beam or to a TRP (or RRH)used for transmission of each beam. The area configuration may indicatea geographical area (e.g., a zone, a beam area, a predefined partialarea of a cell (or cell portion)) associated with the beam identifier.The area configuration may include information regarding latitude andlongitude as information indicating the geographical area.

In a case where the UE 2 performs beam selection (or beamdetermination), the beam configuration information may include a beamselection criterion (or beam determination criterion). The beamselection criterion may include, for example, a threshold or an offsetto be applied to a reception quality of the beamformed reference signalobtained by the beam measurement. The reception quality is, for example,received signal strength (e.g., Reference Signal Received Power (RSRP)),received signal quality (e.g., Reference Signal Received Quality (RSRQ),Signal to Noise Ratio (SNR), or Signal to Interference-pulse-Noise Ratio(SINR)).

In a case where the NR NB 1 performs the beam selection, the beamconfiguration information may include a beam reporting criterion. Thebeam reporting criterion may include, for example, a threshold or anoffset to be applied to a reception quality (e.g., received signalstrength, SNR, or SINK) of the beamformed reference signal, which isobtained by the beam measurement.

The beam configuration information may include beam subframeconfiguration information regarding a beam pattern. In higher frequencybands, the number of beams that the NR NB 1 can simultaneously transmitmay be smaller than the number of beams needed to cover a required cellarea. In this case, the NR NB 1 may perform beam sweeping to cover therequired cell area. More specifically, the NR NB 1 sweeps the cell areain the time domain by sequentially activating each of the multiple beamsets that cover different areas in the cell. The beam set here means oneor a plurality of transmission beams 10 formed simultaneously by the NRNB 1.

The beam subframe configuration information may include configurationinformation for beam sweeping by the NR NB 1 (beam sweepingconfiguration). The beam sweeping configuration information may includea beam sweeping pattern in a time domain. The beam sweeping pattern maybe indicated, for example, by a bit map format associated with one orany combination of: an OFDM symbol; a slot consisting of OFDM symbols; asubframe; and a frame. For example, “1” (or “0”) in the bit map mayindicate that signals are transmitted using the correspondingtransmission beam.

The beam subframe configuration information may include informationregarding a beam pattern in the frequency domain, in addition to or inplace of the beam sweeping in the time domain. For example, one beam setmay be associated with a plurality of frequency resources (e.g.,subcarrier, Physical Resource Block (PRB), or sweeping block). That is,signals may be transmitted using different beams on differentpluralities of frequency resources. One sweeping block covers a specificarea in a cell using one active beam.

In the example shown in FIG. 2 , the NR NB 1 uses a plurality of TRPs101A and 101B. Each TRP 101 forms one or more transmission beams 10. Inthe example shown in FIG. 2 , the UE 2 moves among transmission beams 10within one TRP 101. In the example shown in FIG. 2 , the beamconfiguration information may include configurations regarding aplurality of transmission beams 10 in one TRP 101.

In the example shown in FIG. 3 , the NR NB 1 uses a plurality of TRPs101A and 101B. Each TRP forms one or more transmission beams 10. In theexample shown in FIG. 3 , the UE 2 moves from a transmission beam 10Aformed by the TRP 101A to a transmission beam 10B formed by the TRP101B. In the example shown in FIG. 3 , the beam configurationinformation may include configurations regarding one or moretransmission beams 10 formed by each TRP 101 managed by the NR NB 1.

In the example shown in FIG. 4 , the NR NB 1 provides a plurality ofcarriers (i.e., carriers #1, #2, and #3) using a plurality of TRPs 101.In the example shown in FIG. 4 , the coverages of the three carriers #1,#2, and #3 are hierarchically formed in substantially the samegeographical area. The UE 2 supports aggregation of these carriers. Thecarriers provided by the NR NB 1 may belong to different frequency bandsand may use different numerologies (e.g., subcarrier spacing, symbollength, Transmission Time Interval (TTI), and subframe duration). In theexample shown in FIG. 4 , the TRP 101A operates the carrier #1 (i.e.,cell #1) in the 5 GHz band and forms a plurality of transmission beams10A in the carrier #1. The TRP 101B operates the carrier #2 (i.e., cell#2) in the 5 GHz band and forms a plurality of transmission beams 10B inthe carrier #2. Meanwhile, the TRP 101C operates the carrier #3 (i.e.,cell #3) in the 30 GHz band and forms a plurality of transmission beams10C in the carrier #3. As already described above, in order to provide adesired coverage in higher frequency bands, a high antenna gain isrequired to compensate for the path loss. In order to allow the carrier#3 in the 30 GHz band to cover the same cell area as the carriers #1 and#2 in the 5 GHz band, the beam width of the transmission beams 10C inthe 30 GHz band is narrower than the beam width of the transmissionbeams 10A and 10B in the 5 GHz band.

In the example shown in FIG. 4 , the UE 2 or the NR NB 1 may performbeam selection on a carrier-by-carrier basis, that is, within eachcarrier. More specifically, the UE 2 or the NR NB 1 may perform servingbeam selection from the plurality of transmission beams in the carrier#1, serving beam selection from the plurality of transmission beams inthe carrier #2, and serving beam selection from the plurality oftransmission beams in the carrier #3 independently from one another.Alternatively, the UE 2 or the NR NB 1 may perform beam selection on aper-predefined carrier set basis, that is, within a carrier set. Thecarrier set may be a plurality of carriers belonging to the samefrequency band (e.g., the carriers #1 and carrier #2). Alternatively,the carrier set may be a plurality of carriers in which the samenumerology is used. Alternatively, the carrier set may be a plurality ofcarriers in which a plurality of numerologies handled in a similar waybased on a predetermined criterion are used. In the example shown inFIG. 4 , the beam configuration information may include configurationregarding one or more transmission beams 10 formed by each TRP 101managed by the NR NB 1.

FIG. 5 is a sequence diagram showing one example of a procedure for UEmobility between beams. In the example shown in FIG. 5 , the UE 2selects a serving beam. In Step 501, the NR NB 1 transmits a beamconfiguration to the UE 2. In Step 502, the NR NB 1 and the UE 2 performinitial beam selection. In the initial beam selection, the NR NB 1 mayassign an initial serving beam for the UE 2. Alternatively, the UE 2 mayselect an initial serving beam in a manner similar to thebelow-described beam (re)selection.

In Step 503, the UE 2 performs measurement of transmission beamstransmitted from the NR NB 1 in accordance with the beam configuration.Specifically, the UE 2 attempts to receive one or more beamformedreference signals that respectively correspond to one or moretransmission beams assigned in the beam configuration, and measures areception quality of each received beamformed reference signal. The UE 2may measure received signal strength, SNR, or SINR of each beamformedreference signal.

In Step 504, the UE 2 sends a beam reporting to the NR NB 1. The beamreporting includes beam information based on the measurement results inStep 503. In one example, this beam information may indicate thereception qualities of all the beamformed reference signals measured bythe UE 2. Alternatively, this beam information may indicate one orcombination of the reception quality and the beam ID of the beamformedreference signal at which the reception quality measured by the UE 2exceeds a threshold. Since the UE 2 selects a serving beam in theexample shown in FIG. 5 , the beam reporting in Step 504 may be omitted.

Next, the UE 2 and the NR NB 1 perform Option A1 (i.e., Steps 505 and506), Option A2 (i.e., Steps 507 and 508), or Option A3 (i.e., Steps 509and 510) shown in FIG. 5 .

In Option A1, the RRC layer is not involved in the beam selection, andthe Medium Access Control (MAC) sublayer of the UE 2 performs the beamselection. Specifically, in Step 505, the MAC sublayer of the UE 2selects a serving beam. The UE 2 may select a serving beam based on abeam selection criterion included in the beam configuration received inStep 501. As already described above, the beam selection criterion mayinclude a threshold or an offset applied to the reception quality of thebeamformed reference signal. For example, when the reception quality ofthe beamformed reference signal of one transmission beam is larger thanthe reception quality of the beamformed reference signal of the currentserving beam by more than a predetermined threshold, the UE 2 may selectthis transmission beam as a new serving beam. In Step 506, the UE 2transmits to the NR NB 1 a MAC layer message (e.g., beam indicationmessage) indicating the serving beam newly selected by the UE 2. ThisMAC layer message is processed by the MAC sublayer of the NR NB 1. ThisMAC layer message may be a MAC Control Element (CE).

In Option A2, the MAC sublayer of the UE 2 performs the beam selection,and the RRC layer of the UE 2 notifies the NR NB 1 of the selected beam.Specifically, in Step 507, the MAC sublayer of the UE 2 selects aserving beam. The processing in Step 507 may be similar to that in Step505 described above. In Step 508, the UE 2 notifies the NR NB 1 of theserving beam, newly selected by the UE 2, via RRC signaling.

In Option A3, the RRC layer of the UE 2 triggers the MAC sublayer of theUE 2 to perform beam selection, and the RRC layer or MAC sublayer of theUE 2 notifies the NR NB 1 of the selected beam. Specifically, in Step509, the MAC sublayer of the UE 2 performs the serving beam selectionprocessing triggered by the RRC layer of the UE 2. In Step 510, the UE 2notifies the NR NB 1 of the serving beam, newly selected by the UE 2,via RRC signaling or via a MAC sublayer message (e.g., MAC CE).

In Step 511, the NR NB 1 transmits a response message (e.g., beamindication acknowledge message) to the UE 2 in response to receiving thebeam indication message in Step 506, 508, or 510. The transmission ofthe response message in Step 511 may be omitted.

In Step 512, the UE 2 and the NR NB 1 switch the serving beam fortransmission from the NR NB 1 to the UE 2, from the current beam to thenew beam selected by the UE 2. The processing in Step 512 is performedin the MAC sublayer and the physical (PHY) layer. The MAC sublayer ofthe UE 2 instructs the PHY layer of the UE 2 to switch the serving beam.The switching of the (serving) beam may be expressed as changing of the(serving) beam or modification of the (serving) beam.

Along with the switching of the serving beam in Step 512, one or both ofthe NR NB 1 and the UE 2 may perform at least one of the operationslisted below:

Random Access Channel (RACH) procedure;

Power Headroom Report (PHR) transmission by the UE 2;

Flushing of a soft buffer for Hybrid Automatic Repeat reQuest (HARQ);

Re-start of HARQ from initial transmission for not-yet-successful data;

Reset (i.e., stop and re-start from the first) of CSI derivation; and

Reset or re-start of a timer in the MAC sublayer.

The RACH procedure (or random access procedure) is performed for thebeam after the switching, for example, to determine (or adjust) at leastone of transmission timing and transmission power of the uplink, or tosend a scheduling request (SR) for uplink data transmission. Further,the RACH procedure may be used by the network side (NR NB 1) torecognize that the UE 2 has completed the serving beam switching (orthat the UE 2 has moved). The radio resources to be used in the RACHprocedure (e.g., RACH preamble, time/frequency PRACH resource, beamconfiguration) may be indicated in advance by the NR NB 1 to the UE 2via the beam configuration information. Alternatively, withoutperforming the RACH procedure, the UE 2 or the NR NB 1 may determine (oradjust) the transmission timing of uplink signals by calculating it fromthe timing adjustment value before switching (i.e., Timing Advance) onthe basis of the relation between the beam before the switching and thebeam after the switching. Instead, the timing adjustment value (TA), orthe configuration, after the beam switching may be the same as thatbefore the beam switching.

The transmission of a PHR is performed, for example, to determine (oradjust) the uplink transmission power for the beam after the switching.The UE 2 may trigger a PHR when the beam has been switched. In additionor alternatively, the UE 2 may determine whether to transmit a PHRdepending on whether the value of the propagation loss (or path loss)has been changed by an amount greater than a predetermined thresholdspecified by the NR NB 1, due to the beam switching.

With regard to flushing of the soft buffer for HARQ, the UE 2 may flushthe HARQ soft buffer that has been used before the beam switching when,for example, the beam switching has occurred before the UE 2 completesthe reception of downlink (DL) data (or in the middle of receiving thedata). Alternatively, the UE 2 may discard information stored in theHARQ soft buffer in response to receiving new DL data using the sameHARQ process number (#) as before the switching.

With regard to the reset of CSI derivation, the UE 2 may resetcalculation of the Channel Quality Indicator (CQI) for a downlinkreference signal (e.g., beamformed RS) when, for example, the UE 2 hasperformed the beam switching. In this case, the UE 2 may operate so asto derive a valid CQI value within a predetermined period (e.g., n+8,n+24) from the time (e.g., subframe n) when the beam switching has beenperformed.

With regard to the reset or re-start of a timer in the MAC sublayer, theUE 2 (and the NR NB 1) may reset or re-start the timer in the MACsublayer when, for example, the UE 2 (and the NR NB 1) has performed (ordetermined to perform) the beam switching. The timer of in the MACsublayer includes, for example, at least one of: a timer regarding PHR(e.g., periodicPHR-Timer, prohibitPHR-Timer); a timer regardingDiscontinuous Reception (DRX) (e.g., drx-InactivityTimer,drx-RetransmissionTimer); an uplink synchronization timer (i.e.timeAlignmentTimer); a timer regarding a scheduling request (e.g.,sr-ProhibitTimer); and a timer regarding a buffer status report (e.g.,periodicBSR-Timer, prohibitBSR-Timer).

FIG. 6 is a sequence diagram showing another example of the procedurefor UE mobility between beams. In the example shown in FIG. 6 , the NRNB 1 selects a serving beam. In Step 601, the NR NB 1 transmits a beamconfiguration to the UE 2. In Step 602, the NR NB 1 and the UE 2 performinitial beam selection. In the initial beam selection, the NR NB 1 mayassign an initial serving beam for the UE 2 in a manner similar to thebelow-described beam (re)selection. Alternatively, the UE 2 may selectan initial serving beam.

In Step 603, the UE 2 performs measurement of transmission beamstransmitted from the NR NB 1 in accordance with the beam configuration.In Step 604, the UE 2 sends a beam reporting to the NR NB 1. Theprocessing in Steps 603 and 604 may be similar to the processing inSteps 503 and 504.

Next, the UE 2 and the NR NB 1 perform Option B1 (i.e., Steps 605 and606), Option B2 (i.e., Steps 607 and 608), or Option B3 (i.e., Steps 609and 610) shown in FIG. 6 .

In Option B1, the RRC layer is not involved in the beam selection, andthe MAC sublayer of the NR NB 1 performs the beam selection.Specifically, in Step 605, the MAC sublayer of the NR NB 1 selects aserving beam. For example, when the reception quality of the beamformedreference signal of one transmission beam is larger than the receptionquality of the beamformed reference signal of the current serving beamby more than a predetermined threshold, the NR NB 1 may select thistransmission beam as a new serving beam. In Step 606, the NR NB 1transmits to the UE 2 a MAC layer message (e.g., beam indicationmessage) indicating the serving beam newly selected by the NR NB 1. ThisMAC layer message is processed by the MAC sublayer of the UE 2. This MAClayer message may be a MAC CE.

In Option B2, the MAC sublayer of the NR NB 1 performs the beamselection and the RRC layer of the NR NB 1 notifies the UE 2 of theselected beam. Specifically, in Step 607, the MAC sublayer of the NR NB1 selects a serving beam. The processing in Step 607 may be similar tothe above-described processing in Step 605. In Step 608, the NR NB 1notifies the UE 2 of the serving beam, newly selected by the NR NB 1,via RRC signaling.

In Option B3, the RRC layer of the NR NB 1 triggers the MAC sublayer ofthe NR NB 1 to perform beam selection, and the RRC layer or MAC sublayerof the NR NB 1 notifies the UE 2 of the selected beam. Specifically, inStep 609, the MAC sublayer of the NR NB 1 performs the serving beamselection processing triggered by the RRC layer of the NR NB 1. In Step610, the NR NB 1 notifies the UE 2 of the serving beam, newly selectedby the NR NB 1, via RRC signaling or via a MAC sublayer message (e.g.,MAC CE).

In Step 611, the UE 2 transmits a response message (e.g., beamindication acknowledge message) to the NR NB 1 in response to receivingthe beam indication message in Step 606, 608, or 610. The transmissionof the response message in Step 611 may be omitted.

In Step 612, the UE 2 and the NR NB 1 switch the serving beam fortransmission from the NR NB 1 to the UE 2 from the current beam to thenew beam selected by the NR NB 1. The processing in Step 612 isperformed in the MAC sublayer and the physical (PHY) layer. The MACsublayer of the UE 2 instructs the PHY layer of the UE 2 to switch theserving beam.

FIG. 7 is a sequence diagram showing still another example of theprocedure for UE mobility between beams. In the example shown in FIG. 7, the UE 2 moves between beams while the UE 2 is performing aggregationof three carriers shown in FIG. 4 . Accordingly, the carriers #1 and #2are included in a lower frequency band (e.g., 5 GHz band), while thecarrier #3 is included in a higher frequency band (e.g., 30 GHz band).

In Step 701, the NR NB 1 and the UE 2 establish an RRC connection in thecarrier #1 (cell #1). In accordance with the terminology of LTE carrieraggregation, the carrier #1 (cell #1) may be referred to as a primarycell (PCell) or a primary component carrier (PCC). In Step 702, the NRNB 1 and the UE 2 perform selection of a serving beam in the carrier #1.The processing in Step 702 may be performed in accordance with theprocedure shown in FIG. 5 or 6 .

In Step 703, the NR NB 1 sends secondary carrier configuration to the UE2 and the UE 2 adds the carriers #2 and #3 as secondary carriers.Accordingly, the UE 2 performs aggregation of the three carriers #1, #2,and #3. In Step 704, the NR NB 1 and the UE 2 perform selection of aserving beam in the carrier #2. In Step 705, the NR NB 1 and the UE 2perform selection of a serving beam in the carrier #3. Each of theprocessing in Step 704 and that in Step 705 may be performed inaccordance with the procedure shown in FIG. 5 or 6 . The order of Steps704 and 705 is not particularly limited. The processing in Steps 704 and705 may be performed along with the processing in Step 703.

In Step 706, re-selection of a serving beam in the carrier #3 isperformed due to, for example, the movement of the UE 2. Since the beamwidth of the transmission beams in the carrier #3 (e.g., 30 GHz band) isnarrower than the beam width of the transmission beams in the carriers#1 and #2 (e.g., 5 GHz band), the beam (re)selection for the carrier #3is likely to occur more frequently than those for the carriers #1 and#2. The processing in Step 706 may be performed in accordance with thecell selection shown in FIG. 5 or 6 (i.e., Option A1, A2, A3, B1, B2, orB3).

The (re)selection of the serving beam for the UE 2 by the NR NB 1 may beperformed based on an uplink signal transmitted by the UE 2. This uplinksignal may be, for example, an uplink reference signal (e.g., SRS,beamformed SRS), or signaling such as a RACH preamble. The (re)selectionand switching of the serving beam may be performed independently for theuplink beam and the downlink beam, or those for the uplink beam may beperformed together with those for the downlink beam. Further oralternatively, the relation between the uplink beam (or beam set) andthe downlink beam (or beam set) may be configured in advance, and whenbeam switching in one of the uplink and the downlink is needed andperformed, beam switching in the other of uplink and downlink may beautomatically performed.

When the NR NB 1 (or one TRP 101) manages a carrier set including aplurality of carriers, the UE 2 or the NR NB 1 may perform one or bothof the beam (re)selection and the beam switching per carrier set at thesame timing. As already described above, the carrier set may be, forexample, a plurality of carriers belonging to the frequency band (e.g.,the carriers #1 and #2 in FIG. 4 ). Alternatively, the carrier set maybe a plurality of carriers in which the same numerology is used.Alternatively, the carrier set may be a plurality of carriers in which aplurality of numerologies handled in a similar way based on apredetermined criterion are used.

Along with one or both of the beam (re)selection and the beam switchingperformed in a specific carrier/cell, the UE 2 or the NR NB 1 mayperform one or both of the beam (re)selection and the beam switchingalso in other carrier(s)/cell(s) included in the same carrier set as thespecific carrier/cell. The specific carrier/cell may be, for example, aprimary cell (PCell), a primary carrier, or an anchor carrier in thecarrier set. Alternatively, in response to the beam switching in anycarrier/cell in the carrier set being triggered, the UE 2 or the NR NB 1may perform one or both of the beam (re)selection and the beam switchingalso in other carrier(s)/cell(s) in this carrier set.

In one example, the UE 2 or the NR NB 1 may perform beam (re)selectionand beam switching in the primary cell (PCell) and then perform beam(re)selection and beam switching also in other carrier(s)/cell(s) (i.e.,a secondary cell (SCell) or a secondary component carrier (SCC)) basedon the results of the beam switching in the primary cell (PCell).

In another example, the UE 2 or the NR NB 1 may perform beam(re)selection and beam switching in the anchor carrier in the carrierset and then perform beam (re)selection and beam switching also in othercarrier(s)/cell(s) in the same carrier set as the anchor carrier basedon the results of the beam switching in the anchor carrier.

In still another example, the UE 2 or the NR NB 1 may perform beam(re)selection and beam switching in any carrier/cell in the carrier set,and then perform, based on the result of the beam switching in thiscarrier, beam (re)selection and beam switching also in othercarrier(s)/cell(s) in this carrier set.

As will be understood from the above description, this embodimentprovides several procedures for UE mobility between beams. The UE 2 orthe NR NB 1 performs the selection of a serving beam in the layer 2(e.g., the MAC sublayer). Further, when the UE 2 performs aggregation ofa plurality of carriers, the UE 2 or the NR NB 1 may perform beamselection on a carrier-by-carrier basis, that is, in each carrier.Alternatively, the UE 2 or the NR NB 1 may perform beam selection on aper-predefined carrier set basis, that is, in a carrier set. The carrierset may be, for example, a plurality of carriers belonging to the samefrequency band (e.g., the carriers #1 and carrier #2). Alternatively,the carrier set may be a plurality of carriers in which the samenumerology is used. Alternatively, the carrier set may be a plurality ofcarriers in which a plurality of numerologies handled in a similar waybased on a predetermined criterion are used.

Second Embodiment

This embodiment describes in more detail a case in which the UE 2performs aggregation of multiple carriers with different numerologies.FIG. 8 is a diagram showing one example of a user plane protocol stackfor aggregation of carriers with different numerologies. The layer 2incudes a PDCP layer 801, an RLC layer 802, and a MAC layer. In theexample shown in FIG. 8 , a single MAC entity 803 supports theaggregation of multiple carriers with different numerologies.Accordingly, in the example shown in FIG. 8 , in a way similar to thatin LTE CA, the multi-carrier nature of the physical layer is exposedonly to the MAC layer in which HARQ entities are required for therespective carriers (or serving cells). Each HARQ entity of the MACentity 803 is associated with the PHY layer 804 of a respective one ofthe carriers.

The MAC entity 803 performs one or both of the serving beam selectionand the serving beam switching. The MAC entity 803 may suspend or stopat least part of the MAC (and PHY) processing only for the carrier orcarrier set in which the serving beam switching is to be performed, andthen re-start or newly start this processing after the beam switching.

The 3GPP has studied merger or re-arrangement of several functions usingthe LTE user plane protocol stack as a baseline. For example, the threesublayers of the LTE layer 2 are converged in two sublayers. As shown inFIG. 9 , two new sublayers are referred to as, for example, a higherlayer-2 and a lower layer-2. The higher layer-2 901 includes, forexample, the functions of the PDCP layer 801 and the reordering functionof the RLC layer 802. Meanwhile, the lower layer-2 entity 902 includesthe concatenation function of the RLC layer 802 and the functions of theMAC layer 803. Further, the 3GPP has also studied merger orre-arrangement of the functions of the layer 2 of LTE while maintainingthe three sublayers. For example, the reordering function of the PDCPlayer 801 may be merged with part of the reordering function of the RLClayer 802, or the concatenation function of the RLC layer 802 may beadded to (or re-defined as) the function(s) of the MAC layer. Thisembodiment and the other embodiments can be applied to the NR layer 2even when the configuration of the NR layer 2 is changed from theconfiguration of the existing LTE layer 2.

Third Embodiment

This embodiment describes in more detail a case in which the UE 2performs aggregation of multiple carriers with different numerologies.FIG. 10 is a diagram showing another example of the user plane protocolstack for aggregation of multiple carriers with different numerologies.In the example shown in FIG. 10 , a plurality of MAC entities 1004 areused for aggregation of multiple carriers with different numerologies.Each MAC entity 1004 is associated with one or a plurality of carriers(i.e., carrier set) of one numerology. A PDCP layer 1001 generates PDCPPDUs, while an RLC layer 1002 generates RLC PDUs. The RLC PDUs of asingle bearer or a single flow is routed to one of the MAC entities1004, or may be split and sent to the plurality of MAC entities 1004(1003). Each HARQ entity of each MAC entity 1004 is associated with thePHY layer 1005 of a respective one of the carriers.

When the serving beam selection and the serving beam switching areperformed in a single carrier or a single carrier set, only thecorresponding MAC entity 1004 may perform reset of the MAC (and PHY),update of the configuration information, or reconfiguration.

As described in the second embodiment, the 3GPP has studied merger orre-arrangement of several functions using the LTE user plane protocolstack as a baseline. Accordingly, the protocol stack shown in FIG. 10may be changed as shown in FIG. 11 . In the example shown in FIG. 11 ,the layer 2 includes a higher layer-2 and a lower layer-2. The higherlayer-2 1101 includes, for example, the functions of the PDCP layer 1001and the reordering function of the RLC layer 1002. Meanwhile, the lowerlayer-2 entity 1103 includes the concatenation function of the RLC layer1002 and the functions of the MAC entity 1104.

Fourth Embodiment

This embodiment provides specific examples of configuration andprocessing required for aggregation of multiple carriers with differentnumerologies.

Before the aggregation (i.e., preparation phase), the UE 2 may performRadio Resource Management (RRM) measurement reporting for non-servingcell(s) or deactivated Secondary Component Carrier(s) (SCC(s)) (i.e.,SCell(s)). The UE 2 may further perform beam measurement reporting.

In configuration and activation of the aggregation, the NR NB 1 may sendan instruction to the UE 2 via RRC signaling (e.g.,RRCConnectionReconfiguration message) to perform configuration. In theaggregation of NR carriers, the SCell Activation delay may be defined asfollows. Just for reference, in the LTE carrier aggregation (CA), whenthe UE receives the Activation/Deactivation MAC CE indicating theactivation in the subframe #n, the UE starts a valid Channel QualityIndicator (CQI) feedback no later than the subframe #n+8. In NR, aSCell(s) may be started from an Activated state when it is configured.Instead, in NR, L1/L2 control signaling (e.g., Physical Downlink ControlChannel (PDCCH)) may be used, in place of Activation/Deactivation MACCE, for activation/deactivation of a SCell(s).

Alternatively, in NR, a SCell(s) may be started from a deactivatedstate, similar to the case in LTE. In this case, different SCellActivation delays may be applied to multiple carriers with differentnumerologies. For example, SCell Activation delays that are scaled inaccordance with the difference in their subframe lengths or TTIs may beused for different numerologies. Alternatively, the same SCellActivation delay may be applied to multiple carriers with differentnumerologies.

Some parameters used during the execution of aggregation of multiplecarriers with different numerologies may be defined as follows.

(a) PDCCH Subframe

The PDCCH subframe in which the UE 2 performing Discontinuous Reception(DRX) needs to monitor PDCCH (or to attempt to decode PDCCH) may bedetermined as follows. In accordance with the definition of the LTE, thePDCCH subframe for each numerology may be determined based on thesubframe length that is defined (or derived) from the numerology of thereference carrier (or cell) (e.g., PCell, anchor carrier per carrierset). When the UE 2 performs at least part of the MAC functionality(e.g., DRX) individually for each carrier set, the length of the PDCCHsubframe may differ between the carrier sets.

(b) Power Headroom Report (PHR)

A new PHR format may be defined for aggregation of multiple carrierswith different numerologies. The UE 2 may trigger a PHR when a carrier(cell) with a numerology other than the numerologies of carriers thathave already been added is newly added (e.g., at the time ofconfiguration or activation). In a case where the UE 2 uses a pluralityof MAC entities for aggregation of multiple carriers with differentnumerologies, when a PHR is triggered for a carrier (or cell) managed byany MAC entity, all the MAC entities may transmit PHRs for the carriers(or cells) managed by the respective MAC entities. Alternatively, allthe MAC entities may transmit PHRs for all the carriers (cells) that theUE 2 aggregates.

(c) Scheduling Request (SR), Buffer Status Report (BSR), Physical UplinkControl Channel (PUCCH)

The UE 2 may perform at least one of: SR transmission; BSR transmission;and transmission of the control information, for each carrier set havingthe same numerology. In this case, Data Radio Bearer (DRB) or flow(e.g., Protocol Data Unit (PDU) session) may be restricted in such a waythat it is used only in one carrier set having the same numerology.

(d) Discontinuous Reception (DRX)

At least one of: determination of the Active Time of DRX; determinationof DRX state transition; and configuration of DRX parameters may beperformed per carrier set having the same numerology.

(e) Random Access Channel (RACH)

At least the transmission of a RACH preamble and the transmission andreception of a Random Access Response (RAR) in the Random Accessprocedure may be performed for each carrier set having the samenumerology. Meanwhile, at least part of the Random Access procedure maybe performed using carriers (or carrier sets) having differentnumerologies. In this case, the RAR transmission and reception may beperformed always in a specific reference carrier (or cell) (e.g., PCell,anchor carrier of the carrier set used for the RACH preambletransmission).

(f) Cross-Carrier Scheduling

Cross-carrier scheduling may be performed only within a carrier sethaving the same numerology. On the other hand, when cross-carrierscheduling is performed between carriers (or carrier sets) havingdifferent numerologies, the timing (e.g., slot, subframe or TTI, or theboundary thereof) defined by (or derived from) the carrier (or thenumerology thereof) at the time when downlink control information (e.g.,PDCCH) including downlink (DL) radio resource allocation information oruplink (UL) radio resources-grant is received by the UE 2 may be used asa reference timing to determine the timing of DL data reception or ULdata transmission in the scheduled carrier. Alternatively, the timingdetermined in the scheduled carrier (or the numerology thereof) at thetime when the downlink control information is received by the UE 2 maybe used as the reference timing to determine the timing of DL datareception or UL data transmission.

(g) Round Trip Time (RTT) of HARQ

HARQ RTT for each numerology may be determined based on a TTI (or asubframe length) defined by (or derived from) the numerology of areference carrier (or cell) (e.g., PCell, anchor carrier per carrierset). HARQ RTT in NR may be a value similar to that in LTE (e.g., 5 TTIsin the case of Frequency Division Duplexing (FDD)). Scaling inaccordance with TTI may be applied to HARQ RTT in NR.

The following provides configuration examples of the NR NB 1 and the UE2 according to the above embodiments. FIG. 12 is a block diagram showinga configuration example of the NR NB 1 according to the aboveembodiments. Referring to FIG. 12 , the NR NB 1 includes a RadioFrequency transceiver 1201, a network interface 1203, a processor 1204,and a memory 1205. The RF transceiver 1201 performs analog RF signalprocessing to communicate with the NG UEs including the UE 2. The RFtransceiver 1201 may include a plurality of transceivers. The RFtransceiver 1201 is coupled to an antenna array 1202 and the processor1204. The RF transceiver 1201 receives modulated symbol data from theprocessor 1204, generates a transmission RF signal, and supplies thetransmission RF signal to the antenna array 1202. Further, the RFtransceiver 1201 generates a baseband reception signal based on areception RF signal received by the antenna array 1202, and supplies thebaseband reception signal to the processor 1204. The RF transceiver 1201may include an analog beamformer circuit for beam forming. The analogbeamformer circuit includes, for example, a plurality of phase shiftersand a plurality of power amplifiers.

The network interface 1203 is used to communicate with a network node(e.g., a control node and a transfer node of NG Core). The networkinterface 1203 may include, for example, a network interface card (NIC)conforming to the IEEE 802.3 series.

The processor 1204 performs digital baseband signal processing (i.e.,data-plane processing) and control-plane processing for radiocommunication. The processor 1204 may include a plurality of processors.The processor 1204 may include, for example, a modem processor (e.g., aDigital Signal Processor (DSP)) that performs digital baseband signalprocessing and a protocol stack processor (e.g., a Central ProcessingUnit (CPU) or a Micro Processing Unit (MPU)) that performs thecontrol-plane processing. The processor 1204 may include a digitalbeamformer module for beam forming. The digital beamformer module mayinclude a Multiple Input Multiple Output (MIMO) encoder and a pre-coder.

The memory 1205 is composed of a combination of a volatile memory and anon-volatile memory. The volatile memory is, for example, a StaticRandom Access Memory (SRAM), a Dynamic RAM (DRAM), or any combinationthereof. The non-volatile memory is, for example, a mask Read OnlyMemory (MROM), an Electrically Erasable Programmable ROM (EEPROM), aflash memory, a hard disc drive, or any combination thereof. The memory1205 may include a storage located apart from the processor 1204. Inthis case, the processor 1204 may access the memory 1205 via the networkinterface 1203 or an I/O interface (not shown).

The memory 1205 may store one or more software modules (computerprograms) 1206 including instructions and data to perform processing bythe NR NB 1 described in the above embodiments. In some implementations,the processor 1204 may be configured to load the software modules 1206from the memory 1205 and execute the loaded software modules, therebyperforming processing of the NR NB 1 described in the above embodiments.

FIG. 13 is a block diagram showing a configuration example of the UE 2.A Radio Frequency (RF) transceiver 1301 performs analog RF signalprocessing to communicate with the NR NB 1. The RF transceiver 1301 mayinclude a plurality of transceivers. The analog RF signal processingperformed by the RF transceiver 1301 includes frequency up-conversion,frequency down-conversion, and amplification. The RF transceiver 1301 iscoupled to an antenna array 1302 and a baseband processor 1303. The RFtransceiver 1301 receives modulated symbol data (or OFDM symbol data)from the baseband processor 1303, generates a transmission RF signal,and supplies the transmission RF signal to the antenna array 1302.Further, the RF transceiver 1301 generates a baseband reception signalbased on a reception RF signal received by the antenna array 1302, andsupplies the baseband reception signal to the baseband processor 1303.The RF transceiver 1301 may include an analog beamformer circuit forbeam forming. The analog beamformer circuit includes, for example, aplurality of phase shifters and a plurality of power amplifiers.

The baseband processor 1303 performs digital baseband signal processing(i.e., data-plane processing) and control-plane processing for radiocommunication. The digital baseband signal processing includes (a) datacompression/decompression, (b) data segmentation/concatenation, (c)composition/decomposition of a transmission format (i.e., transmissionframe), (d) channel coding/decoding, (e) modulation (i.e., symbolmapping)/demodulation, and (f) generation of OFDM symbol data (i.e.,baseband OFDM signal) by Inverse Fast Fourier Transform (IFFT).Meanwhile, the control-plane processing includes communicationmanagement of layer 1 (e.g., transmission power control), layer 2 (e.g.,radio resource management and hybrid automatic repeat request (HARD)processing), and layer 3 (e.g., signaling regarding attach, mobility,and call management).

The digital baseband signal processing by the baseband processor 1303may include, for example, signal processing of a Packet Data ConvergenceProtocol (PDCP) layer, a Radio Link Control (RLC) layer, a MAC layer,and a PHY layer. Further, the control-plane processing performed by thebaseband processor 1303 may include processing of a Non-Access Stratum(NAS) protocol, an RRC protocol, and MAC CEs.

The baseband processor 1303 may perform MIMO encoding and pre-coding forbeam forming.

The baseband processor 1303 may include a modem processor (e.g., DSP)that performs the digital baseband signal processing and a protocolstack processor (e.g., a CPU or an MPU) that performs the control-planeprocessing. In this case, the protocol stack processor, which performsthe control-plane processing, may be integrated with an applicationprocessor 1304 described in the following.

The application processor 1304 is also referred to as a CPU, an MPU, amicroprocessor, or a processor core. The application processor 1304 mayinclude a plurality of processors (processor cores). The applicationprocessor 1304 loads a system software program (Operating System (OS))and various application programs (e.g., a call application, a WEBbrowser, a mailer, a camera operation application, and a music playerapplication) from a memory 1306 or from another memory (not shown) andexecutes these programs, thereby providing various functions of the UE2.

In some implementations, as represented by a dashed line (1305) in FIG.13 , the baseband processor 1303 and the application processor 1304 maybe integrated on a single chip. In other words, the baseband processor1303 and the application processor 1304 may be implemented in a singleSystem on Chip (SoC) device 1305. An SoC device may be referred to as asystem Large Scale Integration (LSI) or a chipset.

The memory 1306 is a volatile memory, a non-volatile memory, or acombination thereof. The memory 1306 may include a plurality of memorydevices that are physically independent from each other. The volatilememory is, for example, an SRAM, a DRAM, or any combination thereof. Thenon-volatile memory is, for example, an MROM, an EEPROM, a flash memory,a hard disc drive, or any combination thereof. The memory 1306 mayinclude, for example, an external memory device that can be accessedfrom the baseband processor 1303, the application processor 1304, andthe SoC 1305. The memory 1306 may include an internal memory device thatis integrated in the baseband processor 1303, the application processor1304, or the SoC 1305. Further, the memory 1306 may include a memory ina Universal Integrated Circuit Card (UICC).

The memory 1306 may store one or more software modules (computerprograms) 1307 including instructions and data to perform the processingby the UE 2 described in the above embodiments. In some implementations,the baseband processor 1303 or the application processor 1304 may loadthese software modules 1307 from the memory 1306 and execute the loadedsoftware modules, thereby performing the processing of the UE 2described in the above embodiments with reference to the drawings.

As described above with reference to FIGS. 12 and 13 , each of theprocessors included in the NR NB 1 and the UE 2 according to the aboveembodiments executes one or more programs including instructions tocause a computer to perform an algorithm described with reference to thedrawings. The program(s) can be stored and provided to a computer usingany type of non-transitory computer readable media. Non-transitorycomputer readable media include any type of tangible storage media.Examples of non-transitory computer readable media include magneticstorage media (such as flexible disks, magnetic tapes, hard disk drives,etc.), optical magnetic storage media (e.g., magnetooptical disks),Compact Disc Read Only Memory (CD-ROM), CD-R, CD-R/W, and semiconductormemories (such as mask ROM, Programmable ROM (PROM), Erasable PROM(EPROM), flash ROM, Random Access Memory (RAM), etc.). The program(s)may be provided to a computer using any type of transitory computerreadable media. Examples of transitory computer readable media includeelectric signals, optical signals, and electromagnetic waves. Transitorycomputer readable media can provide the program to a computer via awired communication line (e.g., electric wires, and optical fibers) or awireless communication line.

Other Embodiments

Each of the above-described embodiments may be used individually, or twoor more embodiments may be appropriately combined with one another.

In the above embodiments, the UE 2 may aggregate carriers belonging todifferent frequency bands (e.g., 6 GHz band and 30 GHz band). Thecarriers belonging to different frequency bands may use the samenumerology. That is, in the above embodiments, the NR NB 1 and the UE 2may support aggregation of carriers belonging to different frequencybands and having the same numerology. The UE 2 or the NR NB 1 mayperform beam selection on a per-predefined carrier set basis (i.e.,perform beam selection within a carrier set). The carrier set may be,for example, a plurality of carriers belonging to the same frequencyband.

In the above-embodiments, the operations of the NR NB 1 and the UE 2 maybe applied to a case in which the UE 2 performs Dual Connectivity (e.g.,functions evolved in such a way as to implement an existing DC underInter-RAT environment) of the NR NB 1 and LTE (or eLTE, which is anevolution system of LTE) eNB. When, for example, the (e)LTE eNB isoperated as a Master Node (M-NB) and the NR NB 1 is operated as aSecondary Node (S-NB) for the UE 2, a cell group composed of one or morecells managed by the NR NB 1 may be used as a secondary cell group(SCG). In this case, the above embodiments may be applied to a cell(s)in the SCG. Note that, Dual Connectivity of the NR NB 1 and LTE eNB maybe referred to as Multi Connectivity. Multi Connectivity may beexpressed as an operation mode configured so as to allow a UE includinga plurality of transceivers to use a plurality of radio resourcesprovided by schedulers (of RAN nodes) connected via a non-idealbackhaul.

In the above embodiments, a beam (or a beam set) may be associated witha network slice (NS) in Network Slicing. For example, a plurality ofnetwork slices that satisfy respective different service requirementsmay be configured (or implemented) and these network slices maycorrespond to (or be associated with) respective beams (or respectivebeam sets). In this case, the NR NB 1 and the UE 2 may operate to selecta network slice that corresponds to the service that is being performed(or that will be performed) by the UE 2 and select a beam (or a beamset) that corresponds to the selected network slice. It is thus possibleto select a beam (or a beam set) that is desired by (or optimal to) theUE 2, whereby it is expected that communication characteristics (andservice quality) will be improved.

The above-described embodiments are merely examples of applications ofthe technical ideas obtained by the inventor. These technical ideas arenot limited to the above-described embodiments and various modificationscan be made thereto.

For example, the whole or part of the above embodiments can be describedas, but not limited to, the following supplementary notes.

Supplementary Note 1

A radio terminal comprising:

a wireless transceiver configured to transmit signals to a base stationand receive signals from the base station; and

at least one processor configured to:

-   -   receive beam configuration information from the base station;    -   measure a first plurality of transmission beams transmitted from        the base station in accordance with the beam configuration        information; and    -   use, as a first serving beam for transmission from the base        station to the radio terminal, one or more beams selected from        among the first plurality of transmission beams based on a        measurement result of the first plurality of transmission beams,        wherein

each of the first plurality of transmission beams carries a beamformedreference signal to be measured by the radio terminal, and

the beam configuration information includes reference signalconfiguration indicating a radio resource used on each beam fortransmitting the beamformed reference signal.

Supplementary Note 2

The radio terminal according to Supplementary Note 1, wherein

each of the first plurality of transmission beams carries a signalindicating a beam identifier, and

the beam configuration information indicates the beam identifiers of therespective beams.

Supplementary Note 3

The radio terminal according to Supplementary Note 1 or 2, wherein

the at least one processor is configured to select the first servingbeam from among the first plurality of transmission beams based on themeasurement result of the first plurality of transmission beams, and

the beam configuration information further includes a selectioncriterion of the first serving beam.

Supplementary Note 4

The radio terminal according to Supplementary Note 3, wherein at leastone of selecting of the first serving beam and switching of a servingbeam is performed in a Medium Access Control (MAC) sublayer.

Supplementary Note 5

The radio terminal according to Supplementary Note 1 or 2, wherein theat least one processor is configured to:

transmit, to the base station, beam information based on the measurementresult of the first plurality of transmission beams; and

receive, from the base station, a message indicating the first servingbeam, which is selected by the base station based on the beaminformation.

Supplementary Note 6

The radio terminal according to any one of Supplementary Notes 1 to 5,wherein

the at least one processor is configured to:

measure a second plurality of transmission beams transmitted from thebase station; and

use, as a second serving beam for transmission from the base station tothe radio terminal, one or more beams selected from among the secondplurality of transmission beams based on a measurement result of thesecond plurality of transmission beams,

the first plurality of transmission beams use a first carrier,

the second plurality of transmission beams use a second carrier, and

the at least one processor is further configured to perform aggregationof the first carrier and the second carrier.

Supplementary Note 7

The radio terminal according to Supplementary Note 6, wherein the atleast one processor is configured to, during execution of theaggregation, perform switching of the first serving beam among the firstplurality of transmission beams belonging to the first carrier andperform switching of the second serving beam among the second pluralityof transmission beams belonging to the second carrier.

Supplementary Note 8

The radio terminal according to Supplementary Note 6 or 7, wherein theat least one processor is configured to perform switching of the secondserving beam among the second plurality of transmission beams belongingto the second carrier, in response to switching of the first servingbeam among the first plurality of transmission beams belonging to thefirst carrier being triggered.

Supplementary Note 9

The radio terminal according to any one of Supplementary Notes 6 to 8,wherein the at least one processor is configured to provide a singleMedium Access Control (MAC) entity that performs downlink reception onboth the first serving beam belonging to the first carrier and thesecond serving beam belonging to the second carrier.

Supplementary Note 10

The radio terminal according to Supplementary Note 9, wherein the MACentity is configured to, when switching of a serving beam in the firstcarrier is performed, suspend or stop at least part of MAC layerprocessing for the first carrier but to continue MAC layer processingfor the second carrier.

Supplementary Note 11

The radio terminal according to any one of Supplementary Notes 6 to 8,wherein the at least one processor is configured to provide a first MACentity that performs downlink reception on the first serving beambelonging to the first carrier and provide a second Medium AccessControl (MAC) entity that performs downlink reception on the secondserving beam belonging to the second carrier.

Supplementary Note 12

The radio terminal according to Supplementary Note 11, wherein

the first MAC entity is configured to perform resetting of MAC, updateof configuration information, or re-configuration when switching of aserving beam in the first carrier is performed, and

the second MAC entity is configured to continue MAC layer processingregardless of the switching of the serving beam in the first carrier.

Supplementary Note 13

The radio terminal according to any one of Supplementary Notes 6 to 12,wherein a frequency band in which the first carrier is included isdifferent from a frequency band in which the second carrier is included.

Supplementary Note 14

The radio terminal according to any one of Supplementary Notes 6 to 13,wherein the first carrier and the second carrier are different from eachother in at least one of subcarrier spacing, symbol length, aTransmission Time Interval (TTI), and subframe duration.

Supplementary Note 15

The radio terminal according to any one of Supplementary Notes 1 to 14,wherein the first plurality of transmission beams each carry signalsindicating the same identifiers or the same group identifiers.

Supplementary Note 16

A base station comprising:

at least one wireless transceiver configured to transmit signals to aradio terminal and receive signals from the radio terminal; and

at least one processor configured to:

-   -   transmit beam configuration information to the radio terminal;        and    -   use, as a first serving beam for transmission from the base        station to the radio terminal, one or more beams selected from        among a first plurality of transmission beams transmitted from        the base station based on a result of a measurement by the radio        terminal of the first plurality of transmission beams, wherein

each of the first plurality of transmission beams carries a beamformedreference signal to be measured by the radio terminal, and

the beam configuration information includes reference signalconfiguration indicating a radio resource used on each beam fortransmitting the beamformed reference signal.

Supplementary Note 17

The base station according to Supplementary Note 16, wherein the atleast one processor is configured to receive, from the radio terminal, amessage indicating the first serving beam selected by the radio terminalbased on the measurement result of the first plurality of transmissionbeams.

Supplementary Note 18

The base station according to Supplementary Note 16, wherein the atleast one processor is configured to:

receive, from the radio terminal, beam information based on themeasurement result of the first plurality of transmission beams;

select the first serving beam from among the first plurality oftransmission beams based on the beam information; and

transmit a message indicating the first serving beam selected by thebase station to the radio terminal.

Supplementary Note 19

The base station according to any one of Supplementary Notes 16 to 18,wherein

the at least one processor is configured to use, as a second servingbeam for transmission from the base station to the radio terminal, oneor more beams selected from among a second plurality of transmissionbeams transmitted from the base station based on a result of ameasurement by the radio terminal of the second plurality oftransmission beams,

the first plurality of transmission beams use a first carrier,

the second plurality of transmission beams use a second carrier, and

the at least one processor is further configured to perform aggregationof the first carrier and the second carrier.

Supplementary Note 20

The base station according to Supplementary Note 19, wherein the atleast one processor is configured to, during execution of theaggregation, perform switching of the first serving beam among the firstplurality of transmission beams belonging to the first carrier andperform switching of the second serving beam among the second pluralityof transmission beams belonging to the second carrier.

Supplementary Note 21

The base station according to Supplementary Note 19 or 20, wherein theat least one processor is configured to perform switching of the secondserving beam among the second plurality of transmission beams belongingto the second carrier, in response to switching of the first servingbeam among the first plurality of transmission beams belonging to thefirst carrier being triggered.

Supplementary Note 22

The base station according to any one of Supplementary Notes 19 to 21,wherein the at least one processor is configured to provide a singleMedium Access Control (MAC) entity that performs downlink transmissionon both the first serving beam belonging to the first carrier and thesecond serving beam belonging to the second carrier.

Supplementary Note 23

The base station according to Supplementary Note 22, wherein the MACentity is configured to, when switching of a serving beam in the firstcarrier is performed, suspend or stop at least part of MAC layerprocessing for the first carrier but to continue MAC layer processingfor the second carrier.

Supplementary Note 24

The base station according to any one of Supplementary Notes 19 to 21,wherein the at least one processor is configured to provide a first MACentity that performs downlink transmission on the first serving beambelonging to the first carrier and provide a second Medium AccessControl (MAC) entity that performs downlink transmission on the secondserving beam belonging to the second carrier.

Supplementary Note 25

The base station according to Supplementary Note 24, wherein

the first MAC entity is configured to perform resetting of MAC, updateof configuration information, or re-configuration when switching of aserving beam in the first carrier is performed, and

the second MAC entity is configured to continue MAC layer processingregardless of the switching of the serving beam in the first carrier.

Supplementary Note 26

The base station according to any one of Supplementary Notes 19 to 25,wherein the first carrier and the second carrier are different from eachother in at least one of subcarrier spacing, symbol length, aTransmission Time Interval (TTI), and subframe duration.

Supplementary Note 27

The base station according to any one of Supplementary Notes 16 to 26,wherein the at least one transceiver comprises a plurality ofdistributed Remote Radio Heads (RRHs) or Transmission and ReceptionPoints (TRPs).

Supplementary Note 28

A method for a radio terminal, the method comprising:

receiving beam configuration information from a base station;

measuring a first plurality of transmission beams transmitted from thebase station in accordance with the beam configuration information; and

using, as a first serving beam for transmission from the base station tothe radio terminal, one or more beams selected from among the firstplurality of transmission beams based on a measurement result of thefirst plurality of transmission beams, wherein

each of the first plurality of transmission beams carries a beamformedreference signal to be measured by the radio terminal, and

the beam configuration information includes reference signalconfiguration indicating a radio resource used on each beam fortransmitting the beamformed reference signal.

Supplementary Note 29

A method for a base station, the method comprising:

transmitting beam configuration information to a radio terminal; and

using, as a first serving beam for transmission from the base station tothe radio terminal, one or more beams selected from among a firstplurality of transmission beams transmitted from the base station basedon a result of a measurement by the radio terminal of the firstplurality of transmission beams, wherein

each of the first plurality of transmission beams carries a beamformedreference signal to be measured by the radio terminal, and

the beam configuration information includes reference signalconfiguration indicating a radio resource used on each beam fortransmitting the beamformed reference signal.

Supplementary Note 30

A non-transitory computer readable medium storing a program for causinga computer to perform a method for a radio terminal, wherein the methodcomprises:

receiving beam configuration information from a base station;

measuring a first plurality of transmission beams transmitted from thebase station in accordance with the beam configuration information; and

using, as a first serving beam for transmission from the base station tothe radio terminal, one or more beams selected from among a firstplurality of transmission beams based on a measurement result of thefirst plurality of transmission beams, wherein

each of the first plurality of transmission beams carries a beamformedreference signal to be measured by the radio terminal, and

the beam configuration information includes reference signalconfiguration indicating a radio resource used on each beam fortransmitting the beamformed reference signal.

Supplementary Note 31

A non-transitory computer readable medium storing a program for causinga computer to perform a method for a base station, wherein the methodcomprises:

transmitting beam configuration information to a radio terminal; and

using, as a first serving beam for transmission from the base station tothe radio terminal, one or more beams selected from among a firstplurality of transmission beams transmitted from the base station basedon a result of a measurement by the radio terminal of the firstplurality of transmission beams, wherein

each of the first plurality of transmission beams carries a beamformedreference signal to be measured by the radio terminal, and

the beam configuration information includes reference signalconfiguration indicating a radio resource used on each beam fortransmitting the beamformed reference signal.

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-192329, filed on Sep. 29, 2016, thedisclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

1 NEW RADIO (NR) NODEB (NB)

2 USER EQUIPMENT (UE)

10 BEAM

101 TRANSMISSION AND RECEPTION POINT (TRP)

1204 PROCESSOR

1205 MEMORY

1303 BASEBAND PROCESSOR

1304 APPLICATION PROCESSOR

1306 MEMORY

1. A User Equipment (UE) comprising: a memory; and a processor coupledwith the memory, wherein the processor is configured to: support aCarrier Aggregation (CA) with serving cells including a Primary Cell(PCell) and a Secondary Cell (SCell); receive a Radio Resource Control(RRC) message including a Reference Signal Received Power (RSRP)threshold; and perform a first procedure per serving cell, forindicating a new serving beam to a serving base station, wherein thefirst procedure is performed by a Medium Access Control (MAC) entity,and wherein the first procedure for the PCell includes a selection ofthe serving beam based on the RSRP threshold.
 2. The UE according toclaim 1, wherein the RRC message includes first information indicatingbeams for the first procedure, and wherein the MAC entity is configuredto select the serving beam among the beams.
 3. The UE according to claim1, wherein the MAC entity is configured to perform the first procedurefor the PCell without impacting the first procedure for the SCell.
 4. Amethod of a User Equipment (UE), the method comprising: supporting aCarrier Aggregation (CA) with serving cells including a Primary Cell(PCell) and a Secondary Cell (SCell); receiving a Radio Resource Control(RRC) message including a Reference Signal Received Power (RSRP)threshold; and performing a first procedure per serving cell, forindicating a new serving beam to a serving base station, wherein thefirst procedure is performed by a Medium Access Control (MAC) entity,and wherein the first procedure for the PCell includes a selection ofthe serving beam based on the RSRP threshold.
 5. The method according toclaim 4, wherein the RRC message includes first information indicatingbeams for the first procedure, and wherein the MAC entity is configuredto select the serving beam among the beams.
 6. The method according toclaim 4, wherein the MAC entity is configured to perform the firstprocedure for the PCell without impacting the first procedure for theSCell.